1. Field of the Invention
The present invention relates to a semiconductor chip and a semiconductor device including the same.
2. Description of the Related Art
A package for a semiconductor chip to be installed is sometimes different depending on a user, even if the semiconductor chip is same. For this reason, a designer of the semiconductor chip needs to consider the arrangement of pads in advance so as to permit the semiconductor chip to be installed in various packages. Usually, the pad on the semiconductor chip and a lead of the package is electrically connected through a bonding wire. When the same semiconductor chip is installed on the packages in which the numbers of leads (pins) are different, the numbers of the pads to be connected through the bonding wires to the leads of the packages are different. Thus, there are the pads that are not connected through the bonding wire to the leads of the package, namely, so-called free pads. Since this free pad is in an electrically floating state, a signal applied to the adjacent wiring or other pad may be picked up as noise. Therefore, an internal circuit may be erroneously operated through an input circuit or output circuit connected to the free pad. For this reason, the erroneous operation can be prevented by changing the wiring pattern to be used and pulling up or down a signal line connected to the free pad, depending on the package. However, the position of the free pad is different for each package on which the semiconductor chip is installed, or for each user even if the packages are same. The change of a wiring pattern on the semiconductor chip for each package to be used to pull up and down the free pad increases the manufacture cost of the semiconductor chip. Also, the management cost and delivery time of the semiconductor chip are also increased.
As the technique related to a process for the free pad, a so-called bonding option circuit is known. For example, Japanese Laid Open Patent Application (JP-A-Heisei, 11-17119) discloses a technique in which leakage current is decreased in the bonding option circuit. A bonding option selecting circuit includes an input for receiving a first signal, an output for outputting the first signal, and a switching circuit connected between the input and the output. This switching circuit includes a section for generating a second signal. Also, the switching circuit provides a current path for the first signal. When the second signal is given, the first signal is transferred along the current path. That is, in a case of a free pad being not bonded, in the bonding option selecting circuit, a potential of the pad is fixed by a pull-down circuit composed of a transistor, and a signal of a low level is sent to the internal circuit. When the pad is bounded to a power source, the bonding option selecting circuit operates so as to hold the signal of a high level applied to the pad through a flip-flop in response to a timing signal sent from the internal circuit and send the signal of the high level to the internal circuit, in order to decrease the leak current. Therefore, the bonding option selecting circuit fixedly outputs to the internal circuit, the signal of the level corresponding to the bonded state of the pad. In this way, the signal level of the signal line connected to the free pad can be fixed to prevent an erroneous operation. However, in this circuit, the signal line that is not at the fixed level cannot be connected to the pad.